Elliptic flow of deuterons from simulations with hybrid model

TL;DR

The paper investigates whether deuteron production in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV can be distinguished by the elliptic flow signal using a state-of-the-art hybrid model (TRENTo initial conditions, vHLLE hydro, Hadron Sampler, SMASH afterburner). It compares two production mechanisms—coalescence and direct thermal production—by analyzing the differential elliptic flow $v_2(p_T)$ of deuterons across centralities, alongside $p_T$ spectra. The study finds that coalescence better describes both the deuteron $p_T$ spectra and $v_2(p_T)$, while direct thermal production tends to overshoot the measured $v_2$, and the results differ from earlier simplified-model expectations. The results imply that $v_2$ alone is not a robust discriminator, but the combined behavior of spectra and $v_2$ supports coalescence as the dominant mechanism under the model assumptions, guiding future work on larger clusters and hadronic transport dynamics.

Abstract

Elliptic flow of deuterons is measured on simulated collisions events of Pb+Pb at CMS energy of 2.76 TeV per colliding nucleon pair. We use hybrid model that includes hydrodynamics for the deconfined phase and hadron transport as an afterburner. For deuterons, two production mechanisms are examined: coalescence, and direct thermal production during hadronisation and subsequent transport through the hadronic phase. Differential elliptic flow of deuterons in different centrality bins is evaluated for both implemented production models. In this approach, coalescence describes the experimental data better than direct deuteron production.

Figures (5)

• Figure 1: Transverse momentum spectra of protons (left) and antiprotons (right). Different colours represent different centralities. Except for the most central data, spectra are divided by subsequent factors of $2^n$. Experimental data measured by the ALICE collaboration ALICE:2013mez.
• Figure 2: Same as Fig. \ref{['f:pspec']}, but for positive (left) and negative (right) pions.
• Figure 3: Elliptic flow of identified protons and antiprotons (left) and charged pions (right). Different colors represent different centralities. Experimental data measured by the ALICE collaboration ALICE:2014wao.
• Figure 4: Transverse momentum spectra of deuterons and antideuterons. Different panels show results for different centrality bins. Dotted red line: direct thermal production of deuterons; solid blue line: deuterons built by coalescence. Experimental data by ALICE collaboration ALICE:2015wav.
• Figure 5: Differential elliptic flow of deuterons. Different panels show results for different centrality bins. Red dotted line: predictions from direct thermal production; blue solid line: predictions from coalescence. Bands around the lines indicate statistical uncertainties. Experimental data by the ALICE collaboration ALICE:2017nuf.